I'm using 25mm ERW tube throughout the chassis as I'm putting a V8 in mine and want more strength, I've had to make a few changes where tubes overlap on acute angles but nothing major.
As far as the wishbones are concerned to ensure accuracy and quality, I bought mine from 3ge, and it saves you having to make the jigs too. By the way you get a 10% discount with them for being a member here! See the thread below:
http://www.haynes.co.uk/forums/showthread.php?t=2518